The present invention relates to the field of control engineering, in particular to controlling the operation of a wind turbine. Furthermore, the invention relates to wind turbines having a control system.
The performance of a wind turbine depends on many factors which can be mainly divided into three different classes: ambient conditions, inherent turbine properties and controllable turbine properties. Furthermore, many of those factors are interdependent but the relation therebetween is uncertain or unknown. Since only the controllable turbine properties, e.g. blade pitch, rotor speed, yaw or the like, can be actively influenced by the turbine controller, theoretical turbine models have been developed to predict the turbine response and/or turbine performance for a variety of ambient conditions, inherent turbine properties and respective controller settings.
However, the basis for such theoretical models is uncertain. For example, errors or hidden damages may occur in the manufacturing process, during transport and installation or in the calibration of sensor and controller set points. Furthermore, the inherent properties of the turbine may change over time, e.g. by degradation of the blade surface, loosening of joints or the like. Furthermore, with the use of theoretical models there is a key need to have reliable information about the true ambient conditions like wind speed, wind direction, air density or the like. However, ambient condition data measured by sensors may have systematic errors due to the sensor position at the turbine (e.g. within the slipstream), sensor drift, faulty manufacture or other reasons. Finally, theoretical models are based on several assumptions and, also, have to make approximations to provide a practical implementation of the model. Thus, the theoretical model in itself as well as the input data for the model deviate from the real conditions at a specific turbine at a specific site. As a result, turbine control is not optimal.